Forward simulation of planetary radio occultation plays an
important role in the ongoing advancement of methods for
constructing accurate atmospheric profiles (e.g.,
refractivity) from radio occultation data. In such
simulations, atmospheric parameters and structure are
specified and, hence, are known completely. Therefore, the
forward simulation workbench provides a means for
understanding how specific atmospheric structures affect
real radio occultation experiments and the degree to which
such structures may be accurately reconstructed from
occultation data.

A typical method for simulating radio occultation utilizes
multiple phase screens (MPS). In the MPS method, wave optics
effects such as limb diffraction and diffraction from
sub-Fresnel-scale atmospheric structure have been
successfully represented in simulations for thin atmosphere
occultation. Unfortunately, the traditional MPS simulator
proves less effective in modeling thick atmosphere
occultations. Thick atmospheres refract more strongly than
thin atmospheres and are generally more complex (e.g.,
ducts, critical refraction). As a result of strong
atmospheric refraction, the assumption of straight-line
paths in a given layer is no longer reasonable. This
research describes the limits of the standard MPS approach
in modeling thick atmosphere occultation and presents early
results toward overcoming such limits by accounting for
curved ray paths.